raveling@unify.com (Paul Raveling) (09/12/90)
Raptors. [That's why this is cross-posted to rec.birds, which I don't subscribe to.] Sunday, while soaring near Minden, I had another of those rare encounters with a red-tailed hawk -- with the hawk joining up in the thermal I'd found. I still find it damned exhilarating and take it as a compliment from the expert -- the hawk, that is. In this case lift was good that day, but at the time I'd been cruising through a large area of sink. I headed for a hill that looked like it should trigger a thermal, found one, and started climbing. At about 8,500 feet the hawk joined up. A sign that I'd centered the thermal well was that the hawk flew a smaller circle, concentric with mine, and even briefly flew in formation about 10 meters off my inside wingtip. Note that hawks obey the same safety rule that we sailplane pilots do: Anyone entering a thermal circles in the same direction as whoever is already in it. About a minute later we'd reached 9,500 feet and I'd become so engrossed in watching the hawk that I'd drifted off center. The bird departed, probably grumbling something like "What's that bozo doing?", and used the sailplane pilot's favorite technique of crossing directly through the core of the thermal on the way out. I have nothing but admiration for these feathered folks' flying skills, and they're probably exercising some skills that we're not even aware of. BTW, good thermals were providing solid 800-1,000 fpm climb and were topping out around 15,500 feet. Surface wind was essentially 0, turbulence was VERY light. Minden's looking even better than my old Mojave Desert soaring haunts. ------------------ Paul Raveling Raveling@Unify.com
sandee@sun16 (Daan Sandee) (09/12/90)
In article <1990Sep11.125658@unify.com> raveling@unify.com (Paul Raveling) writes: > Sunday, while soaring near Minden, I had another of those > rare encounters with a red-tailed hawk -- with the hawk joining > up in the thermal I'd found. I still find it damned exhilarating > and take it as a compliment from the expert -- the hawk, that is. That brings back fond memories of long ago ... the same thing happened to me several times, in Europe. My soaring companion then was the Common Buzzard (Buteo buteo). > > A sign that I'd centered the thermal well was that the hawk > flew a smaller circle, concentric with mine, and even briefly > flew in formation about 10 meters off my inside wingtip. Note > that hawks obey the same safety rule that we sailplane pilots do: > Anyone entering a thermal circles in the same direction as > whoever is already in it. > [...] I have nothing but admiration for these > feathered folks' flying skills, and they're probably exercising > some skills that we're not even aware of. But they have those advantages ... what about variable geometry? And those self-adjusting slots at the wingtips? And all those multiple flexible control surfaces at the rear end? Note also that raptors have a trick of extending their landing gear to slow down, something that sailplane pilots wouldn't want to do. Buteos circle at very low speeds - less than 20 mph, I think. This makes for a smaller turning circle, so they can use the core of the thermal ; or, fly a bigger circle at less angle of bank, with a lesser rate of sink. From what I've noticed, their angle of bank is usually somewhat less than a sailplane's. Their gliding performance between thermals is lousy, though ; their cross-country performance can't be much. If a migrating soaring bird meets a headwind, it just gives up and waits for the wind to change. I know there are records of migrating species that average hundreds of miles a day, but they must be wind-assisted. Still, Swainson's Hawk does a 7,000-mile trip twice yearly between the U.S. and Argentina ; in the Old World, White Stork (alas, much less common than formerly) travels between N.W.Europe and Southern Africa, which is about the same distance. Once I had a similar encounter with a gull - I am ashamed to say, I didn't notice which species, but I can assume it was Herring Gull (Larus argentatus). This species circles at a much higher speed - 40 mph, I suppose - because of the much higher wing loading. I got on its tail and was overtaking it ; it kept looking nervously over its shoulder and tried evasive action ; I chased it around the thermal for several minutes (please, no flames ; this was before my birding days, and it was only a stupid gull) and I kept up with it nicely - it had the advantage of mobility and I of speed - until the bird cheated : it started flapping its wings and left me in an upward direction. Another unfair advantage ... > >------------------ >Paul Raveling >Raveling@Unify.com Daan Sandee sandee@sun16.scri.fsu.edu Supercomputer Computations Research Institute Florida State University, Tallahassee, FL 32306-4052 (904) 644-7045
andy@jli.UUCP (Andy Johnson-Laird) (09/13/90)
In article <1990Sep11.125658@unify.com> raveling@unify.com (Paul Raveling) writes: > Sunday, while soaring near Minden, I had another of those > rare encounters with a red-tailed hawk -- with the hawk joining > up in the thermal I'd found. I still find it damned exhilarating > and take it as a compliment from the expert -- the hawk, that is. Yeah! I was soaring just east of Mount Hood about two weeks ago and hit strong thermal at about 1500 agl. I shutdown the engine and retracted it (sorry purists, but it's a selflaunching sailplane) and went on about the business of gaining alttitude. When I got to about 3,700 agl I suddenly noticed I was not alone. There was what we Brits call, a "bloody great bird" in the thermal with me. I would estimate a wing span of at least 6 feet (though it's difficult to get scale at times like this). I remember noting the underside of the bird had lots of white dappling. I also noticed that this BGB (BG bird) was holding....wait for it.... a large *fish* in it's talons. It's talons were positioned "fore and aft" holding the fish with its head towards the front so as to minimize the drag. (Parasitic or Piscine Drag being important to avoid). As Paul says, it's a privilege to soar with birds like this. Typically they only let you stay in the same thermal for one or two turns while they size you up and then decide they really would be rather somewhere else in the sky. THen they flip inverted, extend their talons as dive brakes (I presume) and roll out of the thermal inverted. Has anyone ever seen birds carrying their prey this high off the ground? I found myself wondering what would happen if the bird became alarmed by the 800 lb fibreglass monster and dropped the fish? a) What is the terminal velocity of a fish dropped from 3,700 agl? b) What would the headlines in "The People" read (Earth invaded by spacefish?) As a final thought, how do these marvelous birds find thermals? What do they use as a vario? I can't believe *they* look for sailplanes as a means of finding a thermal! :-) Andy Andy Johnson-Laird ===+=== DG-400 N400YE Johnson-Laird Inc. \|/ ..tektronix!sequent!jli!andy --o-- 850 NW Summit Ave. / \ Portland OR 97210 -------=================( o )=================------ Tel: (503) 274-0784 \ / Fax: (503) 274-0512 O Voicemail 274-0510 Self-launching sailplane pilots do it by themselves.
bob@MorningStar.Com (Bob Sutterfield) (09/13/90)
In the early 80s, the Soaring Society of America's magazine carried a story about a pilot of a Schweizer 1-26 matching performance with a flock of migrating Canada Geese. The geese were soaring a cloud street south and he flew formation just inside the vertex of the "V", their wingtips a constant (very) few feet from his. They flew thus for enough miles that the Schweizer driver got nervous about the return trip home, and broke off the dance.
sandee@sun16.scri.fsu.edu (Daan Sandee) (09/14/90)
In article <933@jli.UUCP> andy@jli.UUCP (Andy Johnson-Laird) writes: >Yeah! I was soaring just east of Mount Hood about two weeks ago >and hit strong thermal at about >1500 agl. I shutdown the engine and retracted it (sorry purists, but it's >a selflaunching sailplane) and went on about the business of gaining alttitude. How I used to hate those things. But that was a long time ago, and I am sure my attitude was of a horseman objecting against the first automobiles ... still, I'm glad my soaring career was over before these damn things became common. >When I got to about 3,700 agl I suddenly noticed I was not alone. >There was what we Brits call, a "bloody great bird" in the thermal with me. >I would estimate a wing span of at least 6 feet (though it's difficult to >get scale at times like this). I remember noting the underside of the bird >had lots of white dappling. I also noticed that this BGB (BG bird) was >holding....wait for it.... a large *fish* in it's talons. A large all-dark bird with a dappled underwing surface is an immature bald eagle. Six feet span would be about right. Great! > >It's talons were positioned "fore and aft" holding the fish with its head >towards the front so as to minimize the drag. (Parasitic or Piscine Drag >being important to avoid). > {..} >Has anyone ever seen birds carrying their prey this high off the ground? Good observation. Ospreys routinely carry their prey aligned fore-and-aft, but I've never seen a bald eagle do so. Ospreys also may fly around with their catch for some time - I've always thought to show off to their mate, and so forth (as part of the courting ritual ospreys give each other nice juicy fish as a present, and they hand it over in mid-air!). But an immature doesn't display or court, and it's a bit early for the breeding season anyway. > >As a final thought, how do these marvelous birds find thermals? What >do they use as a vario? I can't believe *they* look for sailplanes >as a means of finding a thermal! :-) >Andy I've often wondered. In the mountains, they just sit somewhere until they feel a thermal taking off. Also, I've often enough found lift just by the seat of my pants, and I'm sure they can do the same (except they don't have pants, but you see what I mean). P.S. Much as I am delighted to be able to address two of my interests in one posting, I would urge that follow-uppers consider whether their contributions are appropriate to BOTH newsgroups, and post accordingly. Daan Sandee sandee@sun16.scri.fsu.edu Supercomputer Computations Research Institute Florida State University, Tallahassee, FL 32306-4052 (904) 644-7045
raveling@unify.com (Paul Raveling) (09/15/90)
In article <658@sun13.scri.fsu.edu>, sandee@sun16 (Daan Sandee) writes: > In article <1990Sep11.125658@unify.com> raveling@unify.com (Paul Raveling) writes: > But they have those advantages ... what about variable geometry? And those > self-adjusting slots at the wingtips? California Condors may be among the most advanced fliers I've seen. Feathers at their wingtips can splay out into an excellent likeness of winglets to reduce induced drag in slow flight. In the late '70's I saw some in relatively high altitude high speed flight, folding their wings enough to increase wing loading by at least 50% for better cruise efficiency. They might even have been pushing doubled wing loading. It also appears to me that they reduce their wings' camber in cruising flight, just as flapped sailplanes benefit by using negative flaps for cruising. > Buteos circle at very low speeds - less than 20 mph, I think. The hawk who circled with me last weekend appeared to be keeping his speed up to more than what he otherwise would have used. It's possible that hawks use yet another standard practice of safety-conscious soaring pilots: Keeping a speed that allows always easily keeping the neighboring traffic in sight and allowing the traffic to keep you in sight. Of course that's lots easier for the hawk because of its superior field of vision and visual acuity. In this case I was thermaling at 40 knots in about a 45 degree bank, so that my turn radius was about 140 feet. Deriving the hawk's speed from his apparent radius suggests about 30 knots. From past experience of trying to pace red-tailed hawks in a 1-26 I'd estimate that 20-25 knots would be a more natural speed for them, and they can probably fly comfortably at about 15. I haven't yet had a chance to see how fast they fly to penetrate heavy sink. ------------------ Paul Raveling Raveling@Unify.com
raveling@unify.com (Paul Raveling) (09/15/90)
In article <933@jli.UUCP>, andy@jli.UUCP (Andy Johnson-Laird) writes: > In article <1990Sep11.125658@unify.com> raveling@unify.com (Paul Raveling) writes: > When I got to about 3,700 agl I suddenly noticed I was not alone. > There was what we Brits call, a "bloody great bird" in the thermal with me. > I would estimate a wing span of at least 6 feet (though it's difficult to > get scale at times like this). I remember noting the underside of the bird > had lots of white dappling. I also noticed that this BGB (BG bird) was > holding....wait for it.... a large *fish* in it's talons. 6 feet wingspread + fish sounds like a golden eagle. I'm not sure about white dappling on the underside though; anyone know if that's a sign of a young golden eagle? Or do osprey get that large? > a) What is the terminal velocity of a fish dropped from 3,700 agl? I'd guess it would fall head first, stabilized by its tail, and might manage to hit 200+ mph. What a splat that'd make -- Yuch! > b) What would the headlines in "The People" read (Earth invaded by spacefish?) Flying Fish Fall from Fearful Feathered Folk -- Pregnant mermaid suspected of cavorting in sky with reincarnated singer, Elvis Eagle In staid old "Soaring": Flying Fish Sets National Out and Return Record for Submarines ------------------ Paul Raveling Raveling@Unify.com
wwf@oz.plymouth.edu (Dr. Wavell Fogleman) (09/15/90)
Raptors, Osprey Your fish-carrying bird was most likely an Osprey. We spotted one in migration about a week ago carrying a large, 10-12 inch, fish. It seemed to struggle to gain altitude with that load but was last seen heading off to the south with its food to go.
JGHIII@applelink.apple.com (Jack Hodgson) (09/17/90)
In article <933@jli.UUCP> andy@jli.UUCP (Andy Johnson-Laird) writes: > Has anyone ever seen birds carrying their prey this high off the ground? > I found myself wondering what would happen if the bird became alarmed by > the 800 lb fibreglass monster and dropped the fish? > a) What is the terminal velocity of a fish dropped from 3,700 agl? I saw a story a while back about an Alaskan aircraft that suffered a fish strike (!) at some unusually high altitude. They figured the fish was dropped by a higher flying bird. Jack
fiddler@concertina.Eng.Sun.COM (Steve Hix) (09/18/90)
In article <1990Sep14.171720@unify.com>, raveling@unify.com (Paul Raveling) writes: > In article <933@jli.UUCP>, andy@jli.UUCP (Andy Johnson-Laird) writes: > > In article <1990Sep11.125658@unify.com> raveling@unify.com (Paul > Raveling) writes: > > > When I got to about 3,700 agl I suddenly noticed I was not alone. > > There was what we Brits call, a "bloody great bird" in the thermal with me. > > I would estimate a wing span of at least 6 feet (though it's difficult > to get scale at times like this). I remember noting the underside of the > bird had lots of white dappling. I also noticed that this BGB (BG bird) > was holding....wait for it.... a large *fish* in it's talons. > > 6 feet wingspread + fish sounds like a golden eagle. I'm not > sure about white dappling on the underside though; anyone know > if that's a sign of a young golden eagle? Or do osprey get that > large? You Golden eagles have some light marking on their undersides, mostly around the "armpits". Ospreys tend to be lighter-colored, with a wing span approaching 6 feet. (They also tend to hold their wings with a distinctive "crank" about mid-span...looks like it's bent back a bit.) Young Bald eagles look quite a bit like golden eagles, but their feet are clear of feathers, while the golden eagle's feather come down the leg nearly to the foot. Both eagles wingspan's are comfortable over 6 feet...not a condor's 11', but pretty big. -- ------------ The only drawback with morning is that it comes at such an inconvenient time of day. ------------
mjm@oliven.olivetti.com (Michael Mammoser) (09/18/90)
In article <1990Sep14.171720@unify.com>, raveling@unify.com (Paul Raveling) writes: > > 6 feet wingspread + fish sounds like a golden eagle. I'm not > sure about white dappling on the underside though; anyone know > if that's a sign of a young golden eagle? Or do osprey get that > large? Immature Golden Eagles do have some white on the undersides, but it is concentrated at the base of the primaries/secondaries and the tail. I would not describe its effect as "dappled". Also, a Golden Eagle is not likely to be carrying a fish; they are basically hunters of rodents and small mammals. While an Osprey may have a wingspan that approaches 6 feet, its underside could not be described as "dappled" white either. The body is almost totally white, and the wings and tail are mostly white with dark barring. However, the immature Bald Eagle lacks the white head and tail of the adult, but may have extensive white mottling or "dappling" on the underside of the body and wings. This bird is also a "fish-eater" and could be expected to be carrying a fish. Mike